DEPLETION OF ATRIAL NOREPINEPHRINE INDUCED BY RESERPINE IN VITRO

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Abstract
The effects of temperature change in bath fluid and electrical stimulation of the pacemaker area on norepinephrine depletion due to reserpine in vitro were studied in isolated rabbit atria. The results showed that the spontaneous decrease of norepinephrine from rabbit atria was dependent upon temperature, but the reserpine-induced depletion of norepinephrine was not affected by a rise in temperature up to 37[degree]C. A positive correlation did not exist between the decrease in atrial contractile force and the reduction of norepinephrine levels following reserpine administration. It was further demonstrated that atrial norepinephrine levels decreased to a similar degree following direct electrical stimulation as following reserpine in vitro at 30[degree]C, and that stimulation did not potentiate the depleting action of reserpine. The results are compatible with the view that norepinephrine is stored in at least two pools in rabbit atria and suggest that reserpine given in vitro and direct electrical stimulation of the pacemaker area act on the same, probably labile available, portion of the stores of norepinephrine.